People will often not read an entire ad if you lump it all together in one paragraph. They are also much more willing to respect a seller and take their words seriously when proper spelling and grammar is used throughout. I would do it like this:
Lenny is a 4 year old Irish Draft gelding. He stands 16.3hh, and with his bold colour, he is always noticed. He is sired by the Grade A show jumper Cavalier.
Lenny is a very quick learner and has a very willing attitude towards work. He goes nicely in a plain snaffle. He has a brilliant, big, bold jump and has jumped fillers, planks and coloured poles. He has also been schooled around a wide variety of cross country fences including steps, drops, banks, coffins, combinations, styles, logs, tires, etc. He has previously competed at several show jumping and cross country events, and has proved very sensible. He is fantastic in the high-stress atmosphere of show grounds. Lenny would be a fantastic hunting horse as does not mind riding out in a large group.
He is previously being ridden by a 13 year old girl, who jumps, hacks, and schools him herself. He has done beach rides, pleasure rides, and has been on riding holiday. This boy has fantastic manners in and out of the stable. He hacks out alone or in company, and he will happily go first or last. Lenny is fabulous in the heaviest of traffic and is not spooky one bit.
He can be turned out with geldings, mares, and youngsters - I previously turned him out with my 6 month old filly with no problems. He stands for the farrier and stands tied. He is easy to catch, clip, bathe, load and unload. Lenny is a very kind and gentle man who loves attention.
Lenny is microchipped, has an Irish Passport, and is UTD on shots, worming, and trimming. He will go to a good home only - so please, serious inquiries only! Thank you for looking!"
Good luck selling him!